perf: Speed up hit tests for points and markers

If the range tree returns multiple points or markers that might be
within the search area, we were sorting them to maintain a stable
response order.  Javascript sort defaults to a lexical sort which casts
all values to strings, so we had been doing `points.sort((a, b) => a
- b)` to do a numerical sort, but this has a lot of function call
overhead and probably is casting each value between strings and numeric
datatypes.  Instead, we do `points = Uint32Array.from(points).sort();`
which uses native javascript functions and is much faster.

src/markerFeature.js

@@ -228,7 +228,7 @@ var markerFeature = function (arg) {
     // Find markers inside the bounding box
     idx = m_rangeTree.range(min.x, min.y, max.x, max.y);
 
-    idx.sort((a, b) => a - b);
+    idx = Uint32Array.from(idx).sort();
     // Filter by circular region
     idx.forEach(function (i) {
       var d = data[i],
@@ -353,16 +353,20 @@ var markerFeature = function (arg) {
     };
     // Find markers inside the bounding box.  Only these could be in the polygon
     idx = m_rangeTree.range(min.x, min.y, max.x, max.y);
-    // sort by index
-    idx.sort((a, b) => a - b);
+    /* sort by index.  This had been
+     *  idx.sort((a, b) => a - b);
+     * but this requires continual casting from int to str and back, so using
+     * a Uint32Array is faster, though potentially limits the maximum number of
+     * markers. */
+    idx = Uint32Array.from(idx).sort();
     // filter markers within the polygon
     idx.forEach(function (i) {
       var d = data[i];
       let p = m_this.position()(d, i);
-      let rad = radius(data[i], i),
-          swz = scaleWithZoom(data[i], i);
-      const so = strokeOffset(data[i], i),
-          s = swz ? strokeWidth(data[i], i) : 0;
+      let rad = radius(d, i),
+          swz = scaleWithZoom(d, i);
+      const so = strokeOffset(d, i),
+          s = swz ? strokeWidth(d, i) : 0;
       let ris = radiusIncludesStroke(d, i);
       ris = ris === undefined ? true : ris;
       const rwos = ris ? rad + s * (so - 1) / 2 : rad;  // radius without stroke

src/pointFeature.js

@@ -329,7 +329,7 @@ var pointFeature = function (arg) {
     // Find points inside the bounding box
     idx = m_rangeTree.range(min.x, min.y, max.x, max.y);
 
-    idx.sort((a, b) => a - b);
+    idx = Uint32Array.from(idx).sort();
     // Filter by circular region
     idx.forEach(function (i) {
       var d = data[i],
@@ -434,7 +434,7 @@ var pointFeature = function (arg) {
     // Find points inside the bounding box.  Only these could be in the polygon
     idx = m_rangeTree.range(min.x, min.y, max.x, max.y);
     // sort by index
-    idx.sort((a, b) => a - b);
+    idx = Uint32Array.from(idx).sort();
     // filter points within the polygon
     idx.forEach(function (i) {
       var d = data[i],